More than 28,000 people have been killed in drug-related violence since late 2006 [File: Reuters]

At least 11 people have been killed after suspected members of rival drug gangs opened fire on each other at an annual religious festival in Western Mexico.

Machine guns were fired into the packed central square in the small town of Tecalitlan on Friday as people gathered in honour of the Virgin of Guadalupe, one of Mexico's most cherished national and religious symbols.

"During the celebration, a group of subjects arrived in several vehicles to attack another group in the town plaza, sparking a battle," a statement from the attorney general's office in Jalisco state said.

The violence, which also saw a grenade thrown into the crowd, took place as people were preparing to listen to a mariachi concert. Pictures of the aftermath showed overturned chairs in front of a stage.

Panic sparked

The shooting sparked panic in the town, with people afraid to leave their houses and cancelling plans to visit relatives on what is usually a festive holiday across the country, local radio reported.

The statement from the state attorney general's office said police were investigating whether two men found dead in a car outside the town were tied to the shooting.

Mariana Sanchez, Al Jazeera's Mexico correspondent, said that the area was on an important drug trafficking route.

"There is a large number of incidents happening in this state ... where you have the route of the drugs that come from the Pacific, from the south, coming through this state," she said.

"Just three or four months ago, the government forces killed the second-most imporntant drug lord in Mexico, who belonged to the Sinaloa cartel - so what we have are a series of revenge attacks and a turf war that is likely to become much more violent.

Tecalitlan is close to Michoacan state, where Nazario Moreno Gonzalez, the leader of La Familia cartel leader, was reportedly killed during a two-day battle with federal police earlier this week.

Police were still searching for the body of Gonzalez - also known as 'El Chayo' or 'The Doctor - on Saturday after members ofthe gang took away some of the dead from the scene in Apatzingan.

More than 28,000 people have been killed in drug-related violence in Mexico since Felipe Calderon, the president, launched a crackdown on the cartels in late 2006

Source: Al Jazeera and agencies